Calibration device of beam position detector based on spiral line

Abstract

The invention relates to a particle accelerator beam diagnosis technology, and provides a calibration device of a beam position detector based on a spiral line in order to solve the problem that an existing calibration device cannot calibrate the response of the beam position detector to a non-relativistic beam. Comprising a mounting table, a two-dimensional translation table, an electric rotating table, a first through pipe, a second through pipe, a spiral line assembly and a fixed bracket, the beam position detector to be detected is coaxially connected between the first through pipe and the second through pipe; the spiral line assembly is coaxially arranged in an internal space formed by the first through pipe, the to-be-detected beam position detector and the second through pipe; the spiral line assembly comprises a metal cylindrical inner core and an insulating sleeve, a spiral line is wound on the insulating sleeve, flange type SMA connectors are arranged at the two ends of the metal cylindrical inner core, and inner cores of the two flange type SMA connectors are electrically connected with the spiral line; wherein the flange type SMA connector at one end is connected with an external signal generator, and the flange type SMA connector at the other end is connected with a matched load.

Description

Technical Field

[0001] The invention relates to a particle accelerator beam current diagnosis technology, and in particular to a calibration device for a beam current position detector based on a spiral line. Background Art

[0002] The beam position detector (BPM) is one of the most important non-obstructing detectors in the accelerator. The accuracy of its beam position measurement is of great significance for the debugging and optimization of the accelerator. However, due to the influence of errors in processing and assembly, each beam position detector (BPM) needs to be calibrated offline before being installed in the test beam line to obtain its response coefficient to the beam position.

[0003] At present, the wire drawing method or antenna method is usually used to calibrate the beam position detector (BPM) by simulating the electromagnetic field generated by the light-speed beam.

[0004] However, simulation and experimental studies have shown that there is a certain correlation between the response of the beam position detector (BPM) and the relative velocity β of the beam. When the relative velocity β of the beam is small, there is a significant difference between the response of the beam position detector (BPM) and the response to a light-speed beam. The existing calibration device cannot calibrate the response of the beam position detector (BPM) to a non-relativistic beam, and therefore cannot meet the needs of high-precision position measurement. Therefore, how to accurately calibrate the response coefficient of the beam position detector (BPM) installed in the low-energy segment of the accelerator has become the main factor limiting the high-precision position measurement of the BPM in the low-energy segment. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the current calibration device cannot calibrate the response of the beam position detector to the non-relativistic beam, and to propose a calibration device for the beam position detector based on a helical line.

[0006] To achieve the above objectives, the technical solution proposed by the present invention is:

[0007] A calibration device for a beam position detector based on a helical line, which is special in that it comprises a mounting platform, a two-dimensional translation platform fixed on the mounting platform, an electric rotating platform fixed on the two-dimensional translation platform, a first through-tube and a second through-tube coaxially arranged on the electric rotating platform from bottom to top, a helical line assembly and a fixing bracket;

[0008] The apertures of the first through-tube and the second through-tube are both the same as the aperture of the beam position detector to be measured; the beam position detector to be measured is coaxially connected between the first through-tube and the second through-tube; the spiral wire assembly is coaxially arranged in an internal space formed by the first through-tube, the beam position detector to be measured and the second through-tube, for simulating a low-energy beam;

[0009] The spiral wire assembly includes a metal cylindrical inner core and an insulating sleeve sleeved on the metal cylindrical inner core, a spiral wire is wound on the insulating sleeve, flange-type SMA connectors are provided at both ends of the metal cylindrical inner core, and the inner cores of the two flange-type SMA connectors are electrically connected to the spiral wire; the flange-type SMA connector at one end of the metal cylindrical inner core is connected to an external signal generator, and the flange-type SMA connector at this end is installed on an end of the second through tube away from the beam position detector to be measured through the fixed bracket; the flange-type SMA connector at the other end of the metal cylindrical inner core is connected to a matching load for absorbing electromagnetic waves transmitted by the spiral wire assembly.

[0010] Furthermore, the spiral wire is spirally bonded to the insulating sleeve at a fixed interval by epoxy resin glue.

[0011] Furthermore, the fixing bracket includes a supporting crossbar and two supporting vertical bars respectively arranged at both ends of the supporting crossbar, which are used to fix the supporting spiral assembly so that the spiral assembly is coaxial with the first through-tube, the beam position detector to be measured and the second through-tube; the two supporting vertical bars are fixed on the mounting platform;

[0012] One end of the flange-type SMA connector in the spiral wire assembly connected to the external signal generator is installed on the end of the second through-tube away from the beam position detector to be measured through a supporting cross bar; the flange-type SMA connector at the other end of the metal cylindrical inner core is located in the internal space formed by the first through-tube, the beam position detector to be measured, and the second through-tube.

[0013] Furthermore, the characteristic impedance of the spiral wire assembly and the impedance of the matching load are both 50 ohms.

[0014] Furthermore, the flange-type SMA connector is connected to an external signal generator via a radio frequency coaxial line for feeding in radio frequency signals, thereby calibrating the response of the beam position detector to be measured to signals of different frequencies or waveforms.

[0015] Furthermore, the metal cylindrical inner core is a stainless steel cylindrical inner core;

[0016] The spiral wire is a spiral copper strip.

[0017] Furthermore, the propagation speed v of the spiral assembly is p With characteristic impedance Z 0 The following equation is satisfied:

[0018]

[0019] Where: L 0 is the equivalent inductance, C 0 is the equivalent capacitance, β z is the axial phase shift constant, γ is the propagation constant, ∈0 and μ 0 are the vacuum dielectric constant and magnetic permeability respectively, ω is the angular frequency, ∈ r is the relative dielectric constant of the insulating sleeve, I m and K m are the mth first and second modified Bessel functions respectively, a is the outer radius of the insulating sleeve, b is the radius of the first through pipe, d is the radius of the inner core of the metal cylinder, φ=atan(p / 2πa) is the helix angle of the helix, and p is the pitch of the helix.

[0020] Furthermore, the radius of the metal cylindrical inner core, the thickness of the insulating sleeve, the width of the spiral wire and the winding pitch of the spiral wire in the spiral wire assembly are determined according to the propagation speed of the electromagnetic wave along the spiral wire assembly and the characteristic impedance.

[0021] Beneficial effects of the present invention:

[0022] [1] The present invention proposes a calibration device for a beam position detector based on a spiral line, which can calibrate the accurate response of the beam position detector to beams of different speeds and frequencies. The device has a wide range of applications and high calibration accuracy. The spiral line component can achieve a propagation speed that matches the beam and realize slow wave propagation. At the same time, it ensures that the basic characteristics remain unchanged within a large frequency range. The device has good broadband characteristics and can effectively simulate the electromagnetic field generated by a low-energy beam.

[0023] [2] The present invention comprises a spiral wire slow-wave structure composed of a metal cylindrical inner core, an insulating sleeve, a spiral wire and two flange-type SMA connectors, wherein one flange-type SMA connector is connected to an external signal generator through an RF coaxial line to feed in RF signals and thereby obtain the response of the beam position detector to signals of different frequencies or waveforms; the other flange-type SMA connector is connected to a matching load to achieve efficient absorption of electromagnetic waves transmitted by the spiral wire assembly, thereby effectively reducing signal reflection and improving the bandwidth of the calibration device.

[0024] [3] The present invention can realize the translation of the device in two-dimensional space through a two-dimensional translation stage, and can realize the rotation of the beam position detector to be measured through an electric rotating stage, so that the measuring direction of the detector to be measured coincides with the moving direction of the two-dimensional translation stage, which can effectively improve the calibration accuracy; the apertures of the first through-tube and the second through-tube are kept consistent with the aperture of the beam position detector to be measured, which can effectively ensure the continuity of the boundary conditions of the calibration device.

[0025] [4] The present invention can change the propagation speed of electromagnetic waves along the spiral wire assembly by adjusting the radius of the metal cylindrical inner core on the spiral wire assembly, the thickness of the insulating sleeve, the width of the spiral wire and the winding pitch of the spiral wire, simulate beams of different speeds, and then obtain the response of the beam position detector to the beams of different speeds, thereby greatly improving the measurement accuracy and measurement range of the beam position detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of a calibration device of a beam position detector based on a helical line according to the present invention;

[0027] Figure 2 A schematic diagram of the structure of a spiral wire assembly in an embodiment of the present invention;

[0028] Figure 3 is a cross-sectional view of a spiral wire assembly in an embodiment of the present invention;

[0029] Figure 4 Schematic diagram of the phase velocity and characteristic impedance of the helix in the embodiment of the present invention changing with frequency;

[0030] Wherein: (a) is a schematic diagram of the phase velocity of the helix changing with frequency, (b) is a schematic diagram of the characteristic impedance changing with frequency;

[0031] Figure 5 Schematic diagram of radial electric field distribution generated by the spiral line and the low-energy beam in an embodiment of the present invention;

[0032] Figure 6 A schematic diagram showing a comparison between a beam position detector response calibrated by a calibration device in an embodiment of the present invention and a theoretically calculated beam position detector response;

[0033] Reference numerals:

[0034] 1-mounting table, 2-two-dimensional translation table, 3-electric rotation table, 4-first through-tube, 5-second through-tube, 6-fixed bracket, 7-beam position detector, 8-metal cylindrical inner core, 9-insulating sleeve, 10-spiral wire, 11-flange type SMA connector, 12-matching load, 13-support crossbar, 14-support vertical bar. DETAILED DESCRIPTION

[0035] like Figure 1 As shown, a calibration device for a beam position detector based on a helical line comprises a mounting platform 1, a two-dimensional translation platform 2 fixed on the mounting platform 1, an electric rotating platform 3 fixed on the two-dimensional translation platform 2, a first through-tube 4 and a second through-tube 5 coaxially arranged on the electric rotating platform 3 from bottom to top, and a helical line assembly and a fixing bracket 6;

[0036] The calibration device can be translated in the xoy plane by the two-dimensional translation stage 2, and the electric rotating stage 3 is adjusted so that the measuring direction of the detector to be measured coincides with the moving direction of the two-dimensional translation stage;

[0037] The apertures of the first through-tube 4 and the second through-tube 5 are the same as the aperture of the beam position detector 7 to be measured; the beam position detector 7 to be measured is coaxially connected between the first through-tube 4 and the second through-tube 5, ensuring the continuity of the boundary conditions of the calibration device; the end of the first through-tube 4 away from the beam position detector 7 to be measured is fixedly connected to the driving end of the electric rotating stage 3 by bolts;

[0038] The helical wire assembly is coaxially arranged in the internal space formed by the first through-tube 4, the beam position detector 7 to be measured and the second through-tube 5, and is used to simulate a low-energy beam;

[0039] like Figure 2 and Figure 3 As shown, the spiral wire assembly includes a metal cylindrical inner core 8 and an insulating sleeve 9 sleeved on the metal cylindrical inner core 8, a spiral wire 10 is tightly spirally wound on the insulating sleeve 9 at a fixed interval by epoxy resin glue, and flange-type SMA connectors 11 are provided at both ends of the metal cylindrical inner core 8, and the inner cores of the two flange-type SMA connectors 11 are electrically connected to the spiral wire 10 by soldering; the metal cylindrical inner core 8 is a stainless steel cylindrical inner core, the spiral wire 10 is a spiral copper strip, and the insulating sleeve 9 is a polyetheretherketone insulating sleeve;

[0040] The flange type SMA connector 11 at one end of the metal cylindrical inner core 8 is connected to an external signal generator through an RF coaxial line, and is used to feed in RF signals to obtain the response of the BPM to signals of different frequencies or waveforms; the flange type SMA connector 11 at this end is installed on the end of the second through tube 5 away from the beam position detector 7 to be measured through a fixing bracket 6; the flange type SMA connector 11 at the other end of the metal cylindrical inner core 8 is connected to a matching load 12, which is used to absorb electromagnetic waves transmitted by the helical assembly. The impedance of the helical assembly and the impedance of the matching load 12 are both 50 ohms.

[0041] The fixed bracket 6 includes a supporting crossbar 13 and two supporting vertical bars 14 respectively arranged at both ends of the supporting crossbar 13, which are used to fix the supporting spiral assembly so that the spiral assembly is coaxial with the first through tube 4, the beam position detector 7 to be measured and the second through tube 5; the other ends of the two supporting vertical bars 14 are fixed on the mounting platform 1;

[0042] One end of the flange-type SMA connector 11 in the spiral wire assembly connected to the external signal generator is installed on the end of the second through-tube 5 away from the beam position detector 7 to be measured through the supporting cross bar 13; the flange-type SMA connector 11 at the other end of the metal cylindrical inner core 8 is located in the internal space formed by the first through-tube 4, the beam position detector 7 to be measured and the second through-tube 5.

[0043] The propagation speed v of the helical component p With characteristic impedance Z 0 The following equation is satisfied:

[0044]

[0045] Where: L 0 is the equivalent inductance, C 0 is the equivalent capacitance, β z is the axial phase shift constant, γ is the propagation constant, ∈ 0 and μ 0 are the vacuum dielectric constant and magnetic permeability respectively, ω is the angular frequency, ∈ r is the relative dielectric constant of the insulating sleeve 9, I m and K m are the mth first and second modified Bessel functions respectively, a is the outer radius of the insulating sleeve 9, b is the radius of the first through tube 4, d is the radius of the metal cylindrical inner core 8, φ=atan(p / 2πa) is the helix angle of the helix 10, and p is the pitch of the helix 10.

[0046] By adjusting the radius of the metal cylindrical core 8 on the helical wire assembly, the thickness of the insulating sleeve 9, the width of the helix 10 and the winding pitch of the helix 10, the propagation speed of the electromagnetic wave along the helix wire assembly can be changed, the electromagnetic field generated by beams of different energies can be effectively simulated, and the accurate response of the beam position detector 7 to the low-energy beam can be directly measured, which can greatly improve the measurement accuracy and measurement range of the beam position detector 7.

[0047] By deriving and calculating with the above formula and combining with three-dimensional electromagnetic field simulation, it can be deduced that the radius of the metal cylindrical core 8 is 2.4mm, the thickness of the insulating sleeve 9 is 0.9mm, its relative dielectric constant is 3.2, the line width of the metal spiral wire 10 is 2.9mm, the thickness is 0.1mm, and the pitch is 4mm.

[0048] like Figure 4 As shown in (a) and (b), the axial propagation velocity and characteristic impedance of the helical component structure are simulated. It can be seen that the helical component structure can not only realize slow-wave propagation, but also has basically unchanged characteristics within a large frequency range and has broadband characteristics.

[0049] By feeding a Gaussian pulse signal into the helical component structure, such as Figure 5 As shown, the electric field distribution of the calibration device of the present invention at the inner surface of the beam position detector electrode is simulated and compared with the electric field distribution generated by the beam of the same speed obtained by theoretical calculation. It can be seen that the two are highly matched. The calibration method of the present invention can effectively simulate the electric field generated by the low-energy beam; further, as Figure 6 As shown, the response of BPM under the excitation of the spiral structure at different positions is calculated and compared with the actual response characteristics of BPM to low-energy beam. Within the range of 60% aperture (21.6mm), the relative deviation between the two is within 1%, indicating that the present invention can achieve the calibration of BPM response to low-energy beam with higher accuracy.

Claims

1. A calibration device for a beam position detector based on a helical line, characterized in that: It comprises a mounting platform (1), a two-dimensional translation platform (2) fixed on the mounting platform (1), an electric rotating platform (3) fixed on the two-dimensional translation platform (2), a first through pipe (4) and a second through pipe (5) coaxially arranged on the electric rotating platform (3) from bottom to top, as well as a spiral wire assembly and a fixing bracket (6); The apertures of the first through-tube (4) and the second through-tube (5) are both the same as the aperture of the beam position detector (7) to be measured; the beam position detector (7) to be measured is coaxially connected between the first through-tube (4) and the second through-tube (5); the helical wire assembly is coaxially arranged in an internal space formed by the first through-tube (4), the beam position detector (7) to be measured and the second through-tube (5) to simulate a low-energy beam; The spiral wire assembly comprises a metal cylindrical inner core (8) and an insulating sleeve (9) sleeved on the metal cylindrical inner core (8), a spiral wire (10) is wound on the insulating sleeve (9), and flange-type SMA connectors (11) are provided at both ends of the metal cylindrical inner core (8), and the inner cores of the two flange-type SMA connectors (11) are electrically connected to the spiral wire (10); the flange-type SMA connector (11) at one end of the metal cylindrical inner core (8) is connected to an external signal generator, and the flange-type SMA connector (11) at this end is installed on the end of the second through tube (5) away from the beam position detector (7) to be measured through the fixing bracket (6); the flange-type SMA connector (11) at the other end of the metal cylindrical inner core (8) is connected to a matching load (12) for absorbing electromagnetic waves transmitted by the spiral wire assembly.

2. The calibration device of the helical beam position detector according to claim 1, characterized in that: The spiral wire (10) is spirally bonded to the insulating sleeve (9) at a fixed interval by epoxy resin glue.

3. The calibration device of the helical beam position detector according to claim 2, characterized in that: The fixed bracket (6) comprises a supporting crossbar (13) and two supporting vertical bars (14) respectively arranged at two ends of the supporting crossbar (13), and is used to fix the supporting helical wire assembly so that the helical wire assembly is coaxial with the first through tube (4), the beam position detector to be measured (7) and the second through tube (5); the two supporting vertical bars (14) are fixed on the mounting platform (1); One end of the flange-type SMA connector (11) in the spiral wire assembly connected to the external signal generator is installed on the end of the second through-tube (5) away from the beam position detector (7) to be measured through a supporting crossbar (13); the flange-type SMA connector (11) at the other end of the metal cylindrical inner core (8) is located in the internal space formed by the first through-tube (4), the beam position detector (7) to be measured and the second through-tube (5).

4. The calibration device of the helical beam position detector according to claim 3, characterized in that: The characteristic impedance of the helical wire assembly and the impedance of the matching load (12) are both 50 ohms.

5. The calibration device of the helical beam position detector according to claim 4, characterized in that: The flange-type SMA connector (11) is connected to an external signal generator via a radio frequency coaxial line and is used to feed in radio frequency signals, thereby calibrating the response of the beam position detector (7) to be measured to signals of different frequencies or waveforms.

6. The calibration device of the helical beam position detector according to claim 5, characterized in that: The metal cylindrical inner core (8) is a stainless steel cylindrical inner core; The spiral wire (10) is a spiral copper strip.

7. A calibration device for a beam position detector based on a helical line according to any one of claims 1 to 6, characterized in that: The propagation speed v of the helical component p The following equation is satisfied between the characteristic impedance Z0: Where: L0 is the equivalent inductance, C0 is the equivalent capacitance, β z is the axial phase shift constant, γ is the propagation constant, ∈0 and μ0 are the vacuum permittivity and magnetic permeability respectively, ω is the angular frequency, ∈ r is the relative dielectric constant of the insulating sleeve (9), I m and K m are the mth first and second modified Bessel functions respectively, a is the outer radius of the insulating sleeve (9), b is the radius of the first through tube (4), d is the radius of the metal cylindrical inner core (8), φ=atan(p / 2πa) is the helix angle of the helix (10), and p is the pitch of the helix (10).

8. The calibration device of the helical beam position detector according to claim 7, characterized in that: The radius of the metal cylindrical inner core (8), the thickness of the insulating sleeve (9), the width of the spiral wire (10) and the winding pitch of the spiral wire (10) in the spiral wire assembly are determined according to the propagation speed of electromagnetic waves along the spiral wire assembly and the characteristic impedance.

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